Negative electrode and secondary battery

Abstract

A negative electrode including a negative electrode collector and a negative electrode active material layer on the collector. The layer contains a negative electrode active material capable of occluding and releasing lithium. The material in a fully charged state satisfies a conditional expression (1) in 7 Li-MAS-NMR analysis: 0≦( B/A )<0.1  (1), where A represents a sum of integrated area of a first peak and integrated area of a side band peak of the first peak, the first peak indicating a chemical shift in a range of −1 ppm or more and 25 ppm or less with respect to a reference position where a resonant peak of a LiCl aqueous solution having a concentration of 1 mol/dm 3 appears. B represents integrated area of a second peak indicating a chemical shift in a range of 25 ppm or more and 270 ppm or less with respect to the reference position.

What is claimed is: 
     
         1 . A secondary battery comprising:
 a positive electrode;   a negative electrode; and   an electrolyte,   wherein,
 the negative electrode includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material particle including silicon; and 
 the negative electrode active material layer in a fully charged state satisfies a conditional expression (1) below in  7 Li-MAS-NMR analysis
   0≦( B/A )<0.1  (1),
 
 
 where A represents a sum of integrated area of a first peak and integrated area of a side band peak of the first peak, the first peak indicating a chemical shift in a range of −1 ppm or more and 25 ppm or less with respect to a reference position where a resonant peak of a LiCl aqueous solution having a concentration of 1 mol/dm 3  appears, and B represents integrated area of a second peak indicating a chemical shift in a range of 250 ppm or more and 270 ppm or less with respect to the reference position where the resonant peak of a LiCl aqueous solution having a concentration of 1 mol/dm 3  appears, the second peak being different from the side band peak of the first peak. 
   
     
     
         2 . The secondary battery according to  claim 1 , wherein the negative electrode active material particle includes oxygen (O). 
     
     
         3 . The secondary battery according to  claim 2 , wherein the negative electrode active material particle includes carbon (C). 
     
     
         4 . The secondary battery according to  claim 3 , wherein the negative electrode active material particle includes a first oxygen-containing region and a second oxygen-containing region having a higher oxygen content than the first oxygen-containing region. 
     
     
         5 . The secondary battery according to  claim 4 , wherein the positive electrode comprises a positive electrode active material including a composite oxide including lithium, cobalt and nickel. 
     
     
         6 . The secondary battery according to  claim 5 , wherein the electrolyte comprises at least one highly viscous solvent selected from ethylene carbonate or propylene carbonate and at least one lowly viscous solvent selected from dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. 
     
     
         7 . The secondary battery according to  claim 6 , wherein the electrolyte includes at least one of 4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one. 
     
     
         8 . The secondary battery according to  claim 6 , wherein the electrolyte includes vinylene carbonate. 
     
     
         9 . The secondary battery according to  claim 6 , wherein the electrolyte includes at least one of propane sultone or propene sultone. 
     
     
         10 . The secondary battery according to  claim 6 , wherein an oxygen atom in the negative electrode active material particle is bonded to a silicon atom in the negative electrode active material particle. 
     
     
         11 . The secondary battery according to  claim 6 , wherein a content of the oxygen in the negative electrode active material particle is in the range of 3 at % or more and 40 at % or less. 
     
     
         12 . The secondary battery according to  claim 6 , wherein the second oxygen-containing region has a thickness in the range of 100 nm or more and 700 nm or less. 
     
     
         13 . The secondary battery according to  claim 6 , wherein a compound layer including Si—O bond is formed on a surface of the negative electrode active material particle. 
     
     
         14 . The secondary battery according to  claim 13 , wherein the compound layer includes Si—C bond. 
     
     
         15 . The secondary battery according to  claim 13 , wherein the compound layer has a thickness in the range of 10 nm or more and 1,000 nm or less. 
     
     
         16 . The secondary battery according to  claim 6 , wherein the negative electrode active material includes SiC. 
     
     
         17 . The secondary battery according to  claim 6 , wherein the negative electrode active material includes at least one metal element selected from iron, cobalt, nickel, titanium, chromium, or molybdenum. 
     
     
         18 . The secondary battery according to  claim 7 , further comprising a battery can, a safety valve mechanism and a positive temperature coefficient element. 
     
     
         19 . The secondary battery according to  claim 18 , wherein the electrolyte including ethylene carbonate, dimethyl carbonate, 4-fluoro-1,3-dioxolan-2-one, lithium hexafluorophosphate and lithium tetrafluoroborate.